The present invention relates to a towing tractor.
Generally, towing tractors are used, for example, for transportation of cargo in airports. Some tractors are equipped with a motor as a power source and a controller for controlling electric power supply to the motor. The motor and the controller are electrically connected via cables. The motor is connected through a powertrain to an axle so that mechanical power is transmitted from the motor through the powertrain to the axle. The axle is received in an axle housing. The axle housing is supported by a tractor body through a suspension. The suspension allows vertical movement of the axle housing relative to the tractor body.
The axle housing is integrally mounted with the motor and therefore moved vertically together with the motor. The controller is fixedly mounted to the tractor body. When the cable is pulled by vertical movement of the axle housing and the motor relative to the controller, such movement may cause the cable to be tensioned. To prevent this, an example of cable arrangement is disclosed in Japanese Unexamined Patent Application Publication No. 2000-152470.
The publication No. 2000-152470 discloses a hybrid vehicle with such cable arrangement. The vehicle includes a power head (controller) as a stationary object relative to the body and a transaxle case (axle housing) as a movable object relative to the body. The power head is supported by the body through a bracket with relatively high rigidity, and the transaxle case is supported by the body through a bracket with relatively low rigidity. The power head and the transaxle case each has a terminal to which the cable is connected. The length of the cable between the terminals is larger than the shortest distance between the terminals thereby to form an extra length portion in the cable. When the cable is pulled by vertical movement of the transaxle case relative to the power head, the extra length portion of the cable is unbent, thereby preventing the cable from being tensioned.
In the cable arrangement disclosed in the publication No. 2000-152470, the power head has the terminal in its lower surface, and the transaxle case has the terminal in its upper and side surfaces. The cable extends from the upper and side surfaces of the transaxle case toward the lower surface of the power head. In this case, the extra length portion is merely formed in the upwardly extending cable between the power head and the transaxle case located under the power head, by use of the length of the cable extending from the transaxle case to the power head, which makes it difficult to provide the extra length portion of sufficient length in the cable. Thus, when the cable is pulled by vertical movement of the transaxle case, such movement may cause the cable to be tensioned.
The present invention is directed to providing a towing tractor that prevents a cable from being tensioned due to the vertical movement of an axle housing and a motor relative to a controller.